Google Calendar API using refresh token

I have a php app on my site that allows my users to schedule/reschedule calendar events using one of my google calendars, so I don't need the users to authenticate themselves with google. I have worked through getting a token and stored a refresh token but now when I try to access calendar I get an error that says my token has expired. The output is

creating a client
found access token = { "access_token" : "long...token...string", "token_type" : "Bearer", "expires_in" : 3600 }
An error occurred: (0) The OAuth 2.0 access token has expired, and a refresh token is not available. Refresh tokens are not returned for responses that were auto-approved.